1a. Objectives (from AD-416):
Develop catalytic and non-catalytic technologies that enable commercially-viable processes for on-farm scale production of stable and transportable pyrolysis oils that meet boiler fuel or refinable crude oil specifications. Sub-Objective 1: Quantify the effect of various agricultural feedstocks (varying in composition, maturation, post-harvest handling, and pre-treatment) on the pyrolysis process efficiency, kinetics, product yield (pyrolysis oil, syngas, and charcoal), and composition. Sub-Objective 2: Develop commercially preferred catalytic and non-catalytic processes for on-farm scale production of stable and transportable pyrolysis oils that meet specifications as boiler fuel or refinable crude oils. Sub-Objective 3: Develop technologies that enable commercially-viable fast pyrolysis and post-pyrolysis processes for biochar production from a variety of agricultural feedstocks.
1b. Approach (from AD-416):
A stepwise approach will be taken to address the objective by carrying out a series of experiments organized under the three sub-objectives. The first approach will involve screening of biofeedstocks using existing laboratory (desk-top) pyrolysis units to determine their potential use as second generation biomass feedstock. Under this same sub-objective, catalysts with the potential to stabilize pyrolysis liquid, when added to the biomass, will be screened. Under the second sub-objective large scale experiments will be carried out in the ARS fluidized-bed pyrolysis reactor with selected biomass and selected catalysts. Additional experiments will be designed under this sub-objective to explore non-catalytic pathways for producing stabilized pyrolysis oil. The next set of experiments, to be organized under sub-objective 3, will be designed to develop post-pyrolysis processes that will generate biochar with soil-amending, carbon sequestering properties. Modifications, incorporating changes that the experimental outcomes and analyses results will dictate, will be made to the pilot reactor system so as to make it compatible with the distributed scale systems envisioned for the on-farm approach.
3. Progress Report:
Continued to characterize switchgrass for its response to pyrolysis processes. Variables studied included genotype, stage of maturity when harvested and chemical compositions. Work was done in collaboration with NIFA-AFRI funded coordinated agricultural project (CAP) entitled “Sustainable Production and Distribution of Bioenergy for the Central USA (CenUSA)”, located at Iowa State University. Began to characterize various willow clones for their responses to pyrolysis by utilizing analytical pyrolysis methods. This work was done in collaboration with NIFA funded CAP at Penn State, Northeast Woody/Warm-season Biomass Consortium (NewBio). Produced and characterized bio-oil and bio-char at pilot scale from various biomass sources including Brazilian Eucalyptus, consistent with the Embrapa Argoenergy non-funded cooperative research collaboration. Continued to study the pyrolysis of switchgrass/polyhydroxybutyrate (PHB) blends as a model for switchgrass genetically modified to produce PHB. We are successfully producing the valuable chemical crotonic acid from decomposition of PHB, while simultaneously producing bio-oil and bio-char from switchgrass. We have studied the conversion of crotonic acid to butanol, a commodity chemical and potential bio-fuel. We have fractionated, characterized and begun to utilize lignin fractions from bio-oil by testing catalysts to facilitate their further breakdown into useful chemicals. Construction of the two ton per day, Combustion Reduction Integrated Pyrolysis System (CRIPS) for demonstration of on-farm bio-oil production has substantially progressed. Reactor cold flow has been demonstrated. Component parts including liquid collection system have been installed, and the control system has been designed. Mounting of the system on a trailer for transportation to/from consortium of farms has started. Developed a process for producing deoxygenated bio-oil without the use of catalysts by recycling product tail gases to create a reactive atmosphere. This is the subject of a new patent application. Studies on catalytic pyrolysis to produce deoxygenated stable bio-oil have continued into the reporting year. Studies of catalyst deactivation due to deposition of alkali metals have been carried out using switchgrass and the heterogeneous catalyst HZSM-5. A separate reactor for catalytically upgrading pyrolysis vapors (“ex-situ” catalytic pyrolysis) has been tested and subsequently redesigned. More robust catalysts that resist coking are being developed in collaboratortion with consortium members of the NIFA funded Biomass Research & Development Initiative project (FarmBio3) for which we are the principal investigator institution. With FarmBio3 collaborators, we are also developing catalysts that more effectively remove oxygen from bio-oil and have begun studying the effectiveness of these catalysts. We are investigating trends in the chemical composition and the usefulness of biochars for adsorbing heavy metals from water and soils.
1. Production of high quality bio-oil via tail gas recycling. The largest source of feedstock to produce advanced biofuels is non-food biomass, including woody materials, herbaceous grasses and crop residues. One promising process to convert biomass to a liquid is rapid heat treatment (pyrolysis) which produces a product called pyrolysis oil (bio-oil) that can be refined to “green” gasoline and diesel fuels. However, pyrolysis oil is currently incompatible with petroleum for refining because it is corrosive and unstable due largely to the presence of reactive oxygenated molecules. Current methods to produce deoxygenated pyrolysis oil involve adding a catalyst to the process, but this adds complexity and expense to the reactor system. ARS researchers at Wyndmoor, Pennsylvania have developed a process that recycles the tail gas from the pyrolysis reactor and used as reaction medium to influence the incipient pyrolysis process to successfully produce deoxygenated bio-oil without the use of added catalysts. Using this method they have been able to reduce the oxygen content in bio-oil to about a third (from about 35 wt% to about 12 wt%), making this bio-oil a better material for refining into petroleum-like fuels than bio-oil from the standard thermal treatment . This breakthrough was the subject of a patent application filed with the USPTO entitled Method for Producing Bio-oil, (Docket #26512).
Boateng, A.A., Mullen, C.A., Osgood-Jacobs, L., Carlson, P., Macken, N. 2012. Mass balance, energy and exergy analysis of bio-oil production by fast pyrolysis. Journal of Energy Resources Technology. 134/042001-1-9.